Crystalline polymers growth theories

An important consideration of the crystallization process for a crystalline component of a polymer blend is the spherulitic growth rate. The theory for the kinetics of spherulitic growth has been well-established for unblended crystalline polymers with seminal contributions of Hoffman et al. [116-119] The growth rate of the spherulite is controlled by the nucleus formation determined by the undercooling (T — Tg) and the ability of the polymer chains to diffuse to the crystalline surface determined by the difference in T (crystallization temperature) and the Tg. The maximum crystallization rate is in the range of (Tg + Tm)l2. 

Chapter 1 covers experimental techniques widely used in studies of polymer crystalhzation. Chapter 2, Chapter 3, Chapter 4, and Chapter 5 are devoted to the structure of crystalline polymers and also to the kinetics of nucleation and growth of the crystaUine phase. Chapter 6 is focused on molecular modeling of polymer crystallization, whereas Chapter 7 describes overah crystalhzation kinetics, with special reference to the theories widely used in practice. Chapter 8 covers the subject of epitaxy. Chapter 9 is dedicated to melting of polymer crystals. Chapter 10, Chapter 11, and Chapter 13 describe the crystahization in copolymers, miscible and immiscible polymer blends, and also polymer composites. Chapter 12 is focused on phenomena related to the confinement of polymer chains. Chapter 14 describes the effect of flow on crystahization, and finally Chapter 15 covers the crystalhzation in processing conditions. 

The nucleation and growth processes, similar to the situation in low molar mass organic crystals, are dependent on the degree of supereooling of the melt or solution phase. The crystal thickness or alternatively the thiekness of eaeh new crystalline layer in a growing crystal is the one that grows fastest rather than the one that is at equilibrium. There is a wealth of information available on the crystallization of many polymers as well as several theories that aim to prediet the crystallization rates, crystal shapes and lamellar thieknesses. 

The known theories dealing with the overall crystallization kinetics assume that the conversion of amorphous phase into crystalline phase occurs via radial growth of domains—spherulites—in the case of polymers. They do not apply to crystallization processes that do not occur via nucleation and radial growth of domains. 

---